Simultaneous stacking of cationic and anionic compounds in single run capillary zone electrophoresis by two-end field amplified sample injection

In order to extend the application of field amplified sample injection (FASI) in high throughput analysis, a convenient and simple procedure, namely two-end field amplified sample injection (TE-FASI), was developed for the simultaneous stacking of cationic and anionic compounds in a single run capillary zone electrophoresis (CZE). Following the capillary-filling with a buffer of high conductivity, water plug was loaded into each end of the capillary; and two high-field strength zones were generated at both heads of the column when high voltage was applied. Therefore, under suppressed EOF cations and anions can be selectively FASI stacked at anode and cathode head, respectively. After separation, the stacked anions and cations are detected by a common detector placed in the center of the capillary. Under the optimized conditions, the limits of detection for the model cationic (matrine and oxymatrine) and anionic (5-sulfosalicylic acid) compounds were determined as 0.2, 0.2 and 0.06 ng/mL, respectively. Compared with non-stacking conditions, the sensitivities of these compounds were enhanced 1003-, 1330- and 1380-fold, respectively. The results of reproducibility, linearity and real sample analysis show that the proposed procedure is promising to be applied for the simultaneous quantification detection of trace cationic and anionic analytes.     

Arsenic speciation by gradient anion exchange narrow bore ion chromatography and high resolution inductively coupled plasma mass spectrometry detection

Based on gradient anion exchange chromatography (AEC), a new strategy in As-speciation was evaluated. A narrow bore chromatographic system with lower flow rates (≤300 μL) well suitable for the low flow requirements of higher efficiency nebulizers was splitless coupled to a high resolution sector field ICP MS. The AEC system takes full advantage of the detector sensitivity allowing more diluted samples (50–100 times) to be injected, delivering substantially less sample matrix to the column and a lower eluent load to the plasma. The unique plasma compatibility of the NH₄NO₃-eluent salt used in this study enabled high linear salt ramps in gradient applications, highly reproducible retention times (±1%) and detection limits in the low ng/L range. The separation conditions were applied on two different polymeric anion-exchangers: a low capacity, weakly hydrophobic material (AS11, Dionex) and a more frequently used higher capacity, higher hydrophobic material (AS7, Dionex). On both columns, As-species (As(III/V), MMA, DMA, AsB) and Cl⁻ were separated in less than nine minutes and co-elution was circumvented by adapting the separation pH to the optimal column selectivity. The key-advantage of the NH₄NO₃-eluent is that it can adopt any separation pH without compromising the eluent strength which is not possible with all other eluents used so far. The influences of chloride and methanol were investigated and found not to affect the chromatographic performance. Column deposits caused strong reversible As(v) adsorption which reduced As(v) to As(III). A corresponding phosphate excess in the injected sample eliminated the adsorption and prevented artefacts in As(v)/As(III) ratios. The method applied to ground water samples provided robust separations and is compatible with any sample preservation procedure.     

制备方法对掺钡纳米氧化镁负载钌催化剂氨合成性能的影响

 采用普通浸渍法 (CI)、超声-包覆法 (UC) 和超声-静电吸附法 (UEA) 制备了 Ru/Ba-MgO 氨合成催化剂, 并运用高分辨透射电镜、场发射扫描电镜、X 射线粉末衍射、N2 的物理吸附、H2 脉冲化学吸附及程序升温还原等手段对催化剂进行了表征. 结果表明, 在 UEA 样品中, Ba 以静电吸附形式均匀地掺入 MgO 载体中, 因而不仅极大地改善了载体表面形貌, 而且有效地控制了 Ru 晶粒大小, 其平均粒径在 2~3 nm. 该样品中, BaCO3 起始分解温度较低, 低温 BaCO3 含量较高, 因而还原性能较佳. 在 10 MPa, 10 000 h?1 和 425 ºC 条件下, UEA 法制得的 Ru 基催化剂上氨合成反应速率达到 60.42 mmol/(g•h), 分别是 CI 法和 UC 法的 1.9 和 1.1 倍.     

磁场对微乳液法合成聚苯胺结构及其电化学行为的影响

在不同磁场强度下,采用微乳液聚合法合成导电聚苯胺(PANI),以碳纸负载PANI为工作电极,通过循环伏安测试方法,探讨了磁场、氧化剂浓度和聚合时间对微乳液聚合法合成PANI电化学性能的影响;并通过X射线衍射(XRD)、四探针电导率测试和傅立叶红外光谱(FTIR)对产物结构和性能的表征分析,印证了循环伏安分析结果的可靠性.实验结果表明,与无磁条件下制备的PANI相比,磁场条件下制备的PANI具有较高的导电性和规整度;FTIR谱图分析表明,由于磁场的取向作用使分子间相互作用力降低,分子链离域程度增大,使磁场条件下合成PANI的主要特征峰有向低频方向移动的趋势,但分子的基本结构单元没有发生变化.研究结果显示,利用负载PANI的碳纸为工作电极,能够对微乳液法合成PANI的电化学行为进行有效的实时表征.     

土壤颗粒表面电场作用下固-液界面Mg2+-K+与Ca2+-K+交换动力学的比较研究

通过恒流法研究了不同表面电场作用下Mg2+、Ca2+吸附动力学. 结果发现: (1)实验初期阶段是强静电力作用下的零级动力学过程和一定反应时间后的弱静电力作用下的一级动力学过程, 且零级速率过程和一级速率过程之间存在明显的转折点; (2)不同电解质构成中Ca2+的吸附速率明显快于Mg2+的, 平衡吸附量也大于Mg2+的, 且Ca2+在土壤颗粒表面的覆盖度比Mg2+在土壤颗粒表面的覆盖度高; (3)离子的相对有效电荷系数与土壤颗粒表面电场作用的不同是各体系中Ca2+、Mg2+吸附动力学有差别的根本原因; (4)根据离子吸附的理论模型可以分别计算出速率系数、平衡吸附量、离子在土壤颗粒表面的覆盖度以及固定液的体积, 这些参数可以定量评估土壤颗粒表面电场对离子吸附动力学的影响.     

用第一性原理方法获取周期体系中原子的部分电荷

利用量子化学软件包Crystal计算了立方周期性边界条件下液态水体系的静电势(ESP)和静电场(EF).在此基础上,提出了一种由第一性原理方法获取周期体系中原子的部分电荷的快捷方法.该方法把由周期性边界条件引入的平均静电势准mean作为一个拟合参数,通过对第一性原理静电势与Ewald加和法静电势的最小二乘法拟合而实现.值得说明的是,比较静电势与静电场拟合方法,前者的相对拟合误差仅为2%-3%,比后者小一个数量级.考察了四种电荷限制条件下,静电势、静电场拟合的水分子原子部分电荷及偶极矩的分布情况.     

超重力场电沉积NiW合金及其耐碱腐蚀性能

在超重力条件下电沉积NiW合金镀层,考察了超重力对NiW合金电沉积过程(各元素分电流、W含量和槽电压等)的影响规律;并利用扫描电子显微镜(SEM)、Tafel技术和电化学阻抗谱(EIS)技术研究了电沉积NiW合金镀层的表面形貌和在NaOH溶液中的抗腐蚀性能,同时通过浸泡实验考察了镀层的稳定性.结果发现,与常重力条件电沉积的NiW合金相比,超重力场电沉积的NiW合金中W含量增加,镀层表面无微裂纹产生;在10%(w)NaOH溶液中镀层自腐蚀电位正移,自腐蚀电流密度减小,腐蚀电阻也由常重力(重力系数G=1)时的865Ω·cm2增大至超重力(G=256)时的2305Ω·cm2;在10%NaOH溶液中浸泡144h后,超重力场电沉积的NiW合金表面无破碎和起皮现象发生.超重力技术在NiW合金电沉积过程中的应用,使镀层的耐碱腐蚀性能得到改善.     

黄铁矿在维持高放废物处置库近场还原性环境中的作用

研究了黄铁矿受60Coγ射线辐照后对地下水还原性环境的影响.辐照剂量率为200Gy·min-1,总吸收剂量为5×106Gy.通过分析辐照前后以及与地下水共同辐照后黄铁矿的结构和组成,发现60Co的γ射线可使地下水发生辐解反应,从而将黄铁矿氧化;但无论是直接辐照还是与地下水共同辐照,60Co的γ辐射均不改变黄铁矿的结构.黄铁矿可以消耗地下水辐解产生的氧化性产物,有利于维持处置库近场的还原性环境,提高处置库的安全性.     

固相萃取-离子色谱/气相色谱-质谱法联合检测油田水中的有机酸和酚类化合物

建立了固相萃取-离子色谱(IC)/气相色谱-质谱(GC-MS)联合检测高矿化度油田水中低相对分子质量的有机酸和酚类化合物的方法。在中性pH条件下,样品经Waters Oasis HLB柱萃取后,萃取液经稀释、Ag2O沉淀和Ag-H柱处理除去大部分氯离子,再用IC测定有机酸;将萃取柱真空冷冻干燥,然后经甲基叔丁基醚/甲醇(9:1, v/v)脱附并用无水硫酸钠除水,再用GC-MS检测酚类化合物。在优化的实验条件下,4种低相对分子质量的有机酸以及5种酚类化合物的平均加标回收率达到80%以上,相对标准偏差(RSD, n=6)为2.38%～9.45%,定量限均低于88.9 μg/L。该方法测定结果准确可靠,适用于氯离子含量高达150 g/L左右水样中低相对分子质量的有机酸和酚类化合物的检测。